U.K. stocks flipped into the red Monday, with the benchmark FTSE 100 unable to withstand a further selloff in oil prices that in turn weighed on energy producers.

The U.K’s FTSE 100
UKX, +0.33%
fell 1.3% to end at 5,874.06, marking its lowest close since December 2012. The loss was its eighth in a row, the longest string of declines since a 10-day run ended in late August.

British blue-chips had been higher earlier, somewhat recovering from Friday’s 2.2% tumble that left the FTSE 100 with its first close below 6,000 since late September. Contributing to last week’s slump were sharp losses for mining and oil stocks, as prices for energy and metals were shoved lower. Commodity stocks make up about one-fifth of the FTSE 100’s weighting.

Oil blues: Oil prices were pulled further down Monday, pushing West Texas Intermediate crude futures
US:CLF6
below $35 a barrel at one point. Brent crude oil
UK:LCOF6
had tumbled more than 3%, below $37 a barrel. WTI oil did higher in late- afternoon European trade. Still, it faces a roughly 32% fall this year, while Brent has been knocked back by 33%.

“Arguably, the correlation between oil prices and the FTSE is as strong as it ever has been, and with oil breaking towards multiyear lows, this is not a good sign for stocks,” wrote Joshua Mahony, market analyst at IG, in a late Monday note.

BG Group
UK:BG
lost 0.7%. The shares had been higher earlier after regulators in China approved the proposed $70 billion buyout of BG by R. With the go-ahead from China, “all pre-conditional regulatory approvals for the combination have been received and we now move to the next phase,” BG Chief Executive Helge Lund said in a statement.

The early gain for blue-chips following better-than-anticipated industrial production and retail sales reports from China, a major commodities buyer, “is all but forgotten by now, and instead the feeling is that markets are nervously preparing for the Fed decision,” said Mahony. “For that reason, the choppiness seen today could provide a format for future trading as we head into Wednesday’s announcement.”

Investors worldwide are waiting to hear if the U.S. central bank will decide to raise ultralow interest rates for the first time in a decade. Markets are pricing in the possibility of a rate hike. A decision is due after trading closes Wednesday in Europe.

Other notable movers: Miners suffered again. Anglo American PLC
AAL, -2.49%
finished down 4.2%, with S&P Ratings Services warning the platinum and iron ore producer that it may cut its credit rating further.

“[We could lower the ratings within approximately two months unless we see a recovery in prices or sufficiently predictable benefits from the company’s counter measures,” said S&P. Fitch and Moody’s since Thursday have also cut ratings on Anglo American.

But insurer Old Mutual
OML, +0.82%
rose 1.4% after South African President Jacob Zuma unexpectedly named Pravin Gordhan as finance minister Sunday night. Mondi PLC
MNDI, -1.47%
finished roughly unchanged, as gains faded. Old Mutual and Mondi have operations in South Africa, which was rocked by Zuma’s abrupt switching of finance ministers three times in a week.

“Gordhan is an old-hand and much more of a proven entity” than David van Rooyen, the legislator named as finance minister to replace the fired Nhlanhla Nene, said Jasper Lawler, market analyst at CMC Markets, in a note. “Old Mutual and Mondi regained some of last week’s losses on the news but the associated political instability could keep them under pressure,” Lawler added.

Gordhan had served as South Africa’s finance minister between 2009 and 2014.

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